Yeah I know these are used for counting vehicles but can they also be used for detecting vehicle speed?
Description: two pneumatic hoses, affixed to a road. They lead to a box that’s locked to a telephone pole. Location is southern California. On a minor artery road.
Doubtful that it’s to survey if a new stop sign is needed since the next street is minor, dead ends into this one and already has a stop sign. The next intersection with another minor artery already has a stop sign.
Extremely doubtful that a traffic light is being considered since there isn’t anywhere near the amount of traffic to justify one.
This is located on a slope. Many cars speed down here. That’s why I’m wondering about speed sensing by this device.
It’s for a traffic study. For traffic volume and speed.
Depends on the state, but it’s pretty common to to a speed study to see how traffic is flowing. This can result in adjusting the speed limit to match the majority of traffic. Or implement other traffic calming measures if a lower speed is required for some reason.
It could also lead to more enforcement I guess but where I’m from that’s not its intended purpose.
Just wanted to add that California in particular has a law requiring cities to study average speed before they change a speed limit. (And then have to pick a speed that 85% of traffic can follow, unless there are extra safety concerns.)
They measure speed (how long between compression of each hose), direction (which hose was hit first), weight (how much was each hose squeezed), and axel count (how many pairs of wheels went over).
When you are calculating road wear, number of axels (and weight) is more important than number of vehicles.
You can often derive the number and type of vehicles by the pattern of “hits”. A passenger car will have a different pattern than an 18-wheeler; a van will have a longer wheelbase than a motorcycle, etc.
It blew my kond ehen i foind oit that engineers won’t even factor in cars when designing major bridges because they are essentially a rounding error compared to semi-trucks.
The typos started at the precise moment your mind was blown.
Please don’t change them.
Kinda true. Regular cars have an Equivalent Single-Axle Load (ESAL) of 0.0004. Basically, it takes about 9,600 cars to put as much wear on the pavement as one 5-axle Semi.
Similar story for bikes and foot traffic, vs cars IIRC. You can have a staggering number of bikes and foot traffic with very light wear.
Yes, with two hoses they are measuring count, speed, and vehicle weight. Not enforceable, as many others have said - nobody will be getting a speeding ticket from this. It’s just data collection.
Note: force measured on the hoses is a function of vehicle weight and speed. If you only have one hose, you can’t tell the difference between a light vehicle moving fast and a heavy vehicle moving slow. With 2 hoses you can now measure speed, which you can then use along with the pneumatic force to figure out weight.
This sent me down a rabbit hole, now I’m reading a manual on how to calculate the data.
For those interested: https://www.fhwa.dot.gov/policyinformation/pubs/pl18027_traffic_data_pocket_guide.pdf
Allow me to share some personal experiences when setting those up. Nimby’s would approach us and rant about how we were only there to justify a new stop sign or speed bump. A few times we were approached by ding dongs wielding weapons. And every once in a while people like to sabotage or steal the equipment. But once they tamper with the equipment enough times they basically get put on the shit list so their road doesn’t get serviced they don’t get plow service they don’t get anything. Maybe this was their goal maybe not who knows they’re idiots.
Honestly, highway data is used for all kinds of things but mostly for planning repairs, upgrades, and modifications. Redesigning things like intersections, traffic lights, and stop signs are rarely the result of this sort of highway data collection. It’s reported collisions and fatalities that drive safety interventions.
But again, we’re talking about nimby’s who are all fucking idiots.
Thank you for taking the time to reply. This is great information!
Would you share a story or two of your time doing this?
Sure, they’re nothing special, but they were intense at the time. Especially for a bunch of summer interns that had the misfortune of needing to find employment during a recession. I was an engineering student and my cohorts were all in the sciences as well. For being a job that required hammering, measuring, and not getting hit by traffic it was one of the more stimulating jobs I’ve ever worked.
So the typical process for us was to drive to the site, usually it was just a road segment from a list (3-5 year annually rotating lists). We had a truck bed filled with precut hoses, solar powered counting modules, spikes, and then wire mesh hose retainers. We would get the appropriate size hose, slip on retainers, hammer in the spikes, and attach and program the module.
One day a fellow in a pickem’up truck followed us from one road to the next telling us that we had no authority to be there and he would sue if we didn’t take our computers and leave. The next day, at a completely different part of the city (honestly, I have no idea how he found us) he jumped out of his truck and racked a shell in his shotgun. We all just left everything and got in the truck and drove away with him standing there shit talking. The equipment was gone but the police knew the guy. They got our stuff back. They didn’t get my buddies coffee thermos though and he was pretty bent out of shape about that. I think it was old or his dad’s or something. But never saw that guy again.
We would constantly get approached by homeless people who wanted to know what we were doing. I always tried to be as informative as possible but most of the time the basic concept was too confounding. The orange vests were always a problem. One guy asked me why I only have one cone. I still laugh about that today. Just the question. Fucking hilarious. The things you don’t think to ask. It was completely legit too. We were daily put in situations where we were inches from traffic. A single cone and a truck were the only things between oncoming traffic and our faces. Why only one cone? We had to cross roads to attach the hose on the other side. If we require a cone for traffic going this way, why don’t we require one going that way? Is the cone FOR THE TRUCK?!?
What a treasure of a memory that was.
EDIT:
I forgot, there was a contractor who did the leftover work that was occasionally needed the rest of the year, but he was always out of work during the summer and he didn’t like that. So one night I was driving past one of the modules that we set up the week before and there was a frumpy looking guy walking back to his car that was parked very near it on the sidewalk. So the next day I found out who he was from the supervisor and went to the site to check it out. He had unlocked the module and slipped in a piece of paper that just said, “you’re a bitch”. Fucking ROFL.
Since I have neither the time nor the inclination to read it, but I do have a question- can you answer it? Quit record if you just jumped on it? Or you and like five friends?
There’s a timing tolerance you can program. So if you only want to count double axles or get the speed data based on a presumed axle spacing, you can program that in. But, if you feel you must spoof it, listen to the sets of tires as they cross the hose and match that timing while stomping on the hose. You need to stomp pretty hard to get the hose to compress enough and you need to generate an air hammer pressure wave within the hose. This and the intensity is what is measured by the device and recorded as an event.
But these modules are left for weeks to months. So if the counts are all in the, let’s say, 300 range daily but then one single day shows 1000, that day’s data is typically removed from the set. Outliers can happen for all kinds of reasons (e.g. failure, hose break, weather, loss of solar power, unusual or atypical activities, children young and old). So, if the counts are wildly different than prior years’ counts, daily/weekly/monthly inconsistent, beyond comprehension, or obviously defective; they can set up more than one device if they need and some devices can receive more than one input. They can also program the device with multiple inputs to only record data within a specific range of parameters. So there are lots of ways to limit the shenanigans in the data.
And you’d be surprised at how much traffic some roads get. Even some residential roads would see thousands daily. So if you really want to bump up the priority of the road, you would be better off driving over it all day, every day until it was removed; because you’d destroy your leg trying to stomp on it that many times. And you’d have to do this on all adjacent and feeder roads to support that data. And you’d have to ensure that you do this every year until you recognize the desired effects of your endeavor, and then you’d have to continue this practice in perpetuity. Or the jig is up!
I didn’t have any inside knowledge, but I can’t think of what having two would help other than the ability to measure speed. You can count just fine with one.
I should imagine you could measure direction too, if one is tripped before the other.
They may be for calculating speed, but without any further information, there’s no way of telling what wheels belong to what vehicle, or how many wheels (edit: or more specifically, axles) a vehicle has - so it certainly wouldn’t be viable for enforcement.
You can also estimate the size of the vehicle. based on how fast it it going and the time between front and back wheel you could calculate the distance between the wheels.
with two strips you can get a lot more data than if you just have one. count, direction, speed, size, and times the road is active. I dont know if they active measure all that but its possible.
That would be the problem for speed, but for counting you’d just look for close sets of pulses.
Oh, I somehow misread that as you saying you could get speed from just one
